<?php
//$timezone = "Asia/Saigon";
//echo convertSolar2Lunar(11,9,2012,$timezone);
function INT($d) {
	return floor($d);
}

function jdFromDate($dd, $mm, $yy) {
	$a = INT((14 - $mm) / 12);
	$y = $yy + 4800 - $a;
	$m = $mm + 12 * $a - 3;
	$jd = $dd + INT((153 * $m + 2) / 5) + 365 * $y + INT($y / 4) - INT($y / 100) + INT($y / 400) - 32045;
	if ($jd < 2299161) {
		$jd = $dd + INT((153* $m + 2)/5) + 365 * $y + INT($y / 4) - 32083;
	}
	return $jd;
}

function jdToDate($jd) {
	if ($jd > 2299160) { // After 5/10/1582, Gregorian calendar
		$a = $jd + 32044;
		$b = INT((4*$a+3)/146097);
		$c = $a - INT(($b*146097)/4);
	} else {
		$b = 0;
		$c = $jd + 32082;
	}
	$d = INT((4*$c+3)/1461);
	$e = $c - INT((1461*$d)/4);
	$m = INT((5*$e+2)/153);
	$day = $e - INT((153*$m+2)/5) + 1;
	$month = $m + 3 - 12*INT($m/10);
	$year = $b*100 + $d - 4800 + INT($m/10);
	//echo "day = $day, month = $month, year = $year\n";
	return array($day, $month, $year);
}

function getNewMoonDay($k, $timeZone) {
	$T = $k/1236.85; // Time in Julian centuries from 1900 January 0.5
	$T2 = $T * $T;
	$T3 = $T2 * $T;
	$dr = M_PI/180;
	$Jd1 = 2415020.75933 + 29.53058868*$k + 0.0001178*$T2 - 0.000000155*$T3;
	$Jd1 = $Jd1 + 0.00033*sin((166.56 + 132.87*$T - 0.009173*$T2)*$dr); // Mean new moon
	$M = 359.2242 + 29.10535608*$k - 0.0000333*$T2 - 0.00000347*$T3; // Sun's mean anomaly
	$Mpr = 306.0253 + 385.81691806*$k + 0.0107306*$T2 + 0.00001236*$T3; // Moon's mean anomaly
	$F = 21.2964 + 390.67050646*$k - 0.0016528*$T2 - 0.00000239*$T3; // Moon's argument of latitude
	$C1=(0.1734 - 0.000393*$T)*sin($M*$dr) + 0.0021*sin(2*$dr*$M);
	$C1 = $C1 - 0.4068*sin($Mpr*$dr) + 0.0161*sin($dr*2*$Mpr);
	$C1 = $C1 - 0.0004*sin($dr*3*$Mpr);
	$C1 = $C1 + 0.0104*sin($dr*2*$F) - 0.0051*sin($dr*($M+$Mpr));
	$C1 = $C1 - 0.0074*sin($dr*($M-$Mpr)) + 0.0004*sin($dr*(2*$F+$M));
	$C1 = $C1 - 0.0004*sin($dr*(2*$F-$M)) - 0.0006*sin($dr*(2*$F+$Mpr));
	$C1 = $C1 + 0.0010*sin($dr*(2*$F-$Mpr)) + 0.0005*sin($dr*(2*$Mpr+$M));
	if ($T < -11) {
		$deltat= 0.001 + 0.000839*$T + 0.0002261*$T2 - 0.00000845*$T3 - 0.000000081*$T*$T3;
	} else {
		$deltat= -0.000278 + 0.000265*$T + 0.000262*$T2;
	};
	$JdNew = $Jd1 + $C1 - $deltat;
	//echo "JdNew = $JdNew\n";
	return INT($JdNew + 0.5 + $timeZone/24);
}

function getSunLongitude($jdn, $timeZone) {
	$T = ($jdn - 2451545.5 - $timeZone/24) / 36525; // Time in Julian centuries from 2000-01-01 12:00:00 GMT
	$T2 = $T * $T;
	$dr = M_PI/180; // degree to radian
	$M = 357.52910 + 35999.05030*$T - 0.0001559*$T2 - 0.00000048*$T*$T2; // mean anomaly, degree
	$L0 = 280.46645 + 36000.76983*$T + 0.0003032*$T2; // mean longitude, degree
	$DL = (1.914600 - 0.004817*$T - 0.000014*$T2)*sin($dr*$M);
	$DL = $DL + (0.019993 - 0.000101*$T)*sin($dr*2*$M) + 0.000290*sin($dr*3*$M);
	$L = $L0 + $DL; // true longitude, degree
	//echo "\ndr = $dr, M = $M, T = $T, DL = $DL, L = $L, L0 = $L0\n";
    // obtain apparent longitude by correcting for nutation and aberration
    $omega = 125.04 - 1934.136 * $T;
    $L = $L - 0.00569 - 0.00478 * sin($omega * $dr);
	$L = $L*$dr;
	$L = $L - M_PI*2*(INT($L/(M_PI*2))); // Normalize to (0, 2*PI)
	return INT($L/M_PI*6);
}

function getLunarMonth11($yy, $timeZone) {
	$off = jdFromDate(31, 12, $yy) - 2415021;
	$k = INT($off / 29.530588853);
	$nm = getNewMoonDay($k, $timeZone);
	$sunLong = getSunLongitude($nm, $timeZone); // sun longitude at local midnight
	if ($sunLong >= 9) {
		$nm = getNewMoonDay($k-1, $timeZone);
	}
	return $nm;
}

function getLeapMonthOffset($a11, $timeZone) {
	$k = INT(($a11 - 2415021.076998695) / 29.530588853 + 0.5);
	$last = 0;
	$i = 1; // We start with the month following lunar month 11
	$arc = getSunLongitude(getNewMoonDay($k + $i, $timeZone), $timeZone);
	do {
		$last = $arc;
		$i = $i + 1;
		$arc = getSunLongitude(getNewMoonDay($k + $i, $timeZone), $timeZone);
	} while ($arc != $last && $i < 14);
	return $i - 1;
}

/* Comvert solar date dd/mm/yyyy to the corresponding lunar date */
function convertSolar2Lunar($dd, $mm, $yy, $timeZone) {
	$dayNumber = jdFromDate($dd, $mm, $yy);
	$k = INT(($dayNumber - 2415021.076998695) / 29.530588853);
	$monthStart = getNewMoonDay($k+1, $timeZone);
	if ($monthStart > $dayNumber) {
		$monthStart = getNewMoonDay($k, $timeZone);
	}
	$a11 = getLunarMonth11($yy, $timeZone);
	$b11 = $a11;
	if ($a11 >= $monthStart) {
		$lunarYear = $yy;
		$a11 = getLunarMonth11($yy-1, $timeZone);
	} else {
		$lunarYear = $yy+1;
		$b11 = getLunarMonth11($yy+1, $timeZone);
	}
	$lunarDay = $dayNumber - $monthStart + 1;
	$diff = INT(($monthStart - $a11)/29);
	$lunarLeap = 0;
	$lunarMonth = $diff + 11;
	if ($b11 - $a11 > 365) {
		$leapMonthDiff = getLeapMonthOffset($a11, $timeZone);
		if ($diff >= $leapMonthDiff) {
			$lunarMonth = $diff + 10;
			if ($diff == $leapMonthDiff) {
				$lunarLeap = 1;
			}
		}
	}
	if ($lunarMonth > 12) {
		$lunarMonth = $lunarMonth - 12;
	}
	if ($lunarMonth >= 11 && $diff < 4) {
		$lunarYear -= 1;
	}
	return array($lunarDay, $lunarMonth, $lunarYear, $lunarLeap);
}

/* Convert a lunar date to the corresponding solar date */
function convertLunar2Solar($lunarDay, $lunarMonth, $lunarYear, $lunarLeap, $timeZone) {
	if ($lunarMonth < 11) {
		$a11 = getLunarMonth11($lunarYear-1, $timeZone);
		$b11 = getLunarMonth11($lunarYear, $timeZone);
	} else {
		$a11 = getLunarMonth11($lunarYear, $timeZone);
		$b11 = getLunarMonth11($lunarYear+1, $timeZone);
	}
	$k = INT(0.5 + ($a11 - 2415021.076998695) / 29.530588853);
	$off = $lunarMonth - 11;
	if ($off < 0) {
		$off += 12;
	}
	if ($b11 - $a11 > 365) {
		$leapOff = getLeapMonthOffset($a11, $timeZone);
		$leapMonth = $leapOff - 2;
		if ($leapMonth < 0) {
			$leapMonth += 12;
		}
		if ($lunarLeap != 0 && $lunarMonth != $leapMonth) {
			return array(0, 0, 0);
		} else if ($lunarLeap != 0 || $off >= $leapOff) {
			$off += 1;
		}
	}
	$monthStart = getNewMoonDay($k + $off, $timeZone);
	return jdToDate($monthStart + $lunarDay - 1);
}
function checkLunarLeap($yy)
{
	if( (($yy % 4 == 0) && ($yy % 100 != 0)) || ($yy % 400 == 0))	
		return 1;
	else
		return 0;
}
$date_array = getdate();
$dd = $_REQUEST['dd'];
$mm = $_REQUEST['mm'];
$yy = $_REQUEST['yy'];
if ($dd == 0) $dd = $date_array['mday'];
if ($mm == 0) $mm = $date_array['mon'];
if ($yy == 0) $yy = $date_array['year'];
//$al = convertSolar2Lunar($dd, $mm, $yy, 7.0);
echo checkLunarLeap($yy);
$al = convertLunar2Solar($dd, $mm, $yy, 0, 7.0);
echo "<p><form action=\"\" method=\"POST\">\n";
echo "Ng&#224;y: <input name=\"dd\" size=2 value=\"$dd\">\n";
echo "Th&#225;ng: <input name=\"mm\" size=2 value=\"$mm\">\n";
echo "N&#259;m: <input name=\"yy\" size=4 value=\"$yy\">\n";
echo "<input type=\"submit\">\n";
echo "</form>\n";

echo "D&#432;&#417;ng l&#7883;ch: $dd/$mm/$yy => ";
$s = "&#194;m l&#7883;ch: $al[0]/$al[1]/$al[2]";
//if ($al[3] == 1) $s = $s . " nhu&#7853;n";
echo "$s\n";
?>